JP4781106B2 - Silicon etching method and apparatus, and etched silicon body - Google Patents

Description

  The present invention relates to a method and apparatus for plasma etching a silicon material in a tapered shape, and an etched silicon body produced by the method and apparatus.

Conventionally, dry etching using plasma has been widely used as an etching method for silicon materials. In the dry etching process using plasma, low-pressure process gas plasma is generated in a reduced-pressure atmosphere, and the silicon material is etched by the generated plasma. In addition, in order to increase the anisotropy of etching, a technique is also known in which an etching gas (for example, SF ₆ ) and a deposition gas (for example, C ₄ F ₈ ) are simultaneously introduced as a process gas to form plasma.

  By the way, in a processing technique to which a MEMS (Micro Electro Mechanical System) technique is applied to a silicon body, an etching process that forms a taper rather than a vertical etching surface is often desired. . As an example of this, a silicon body that has been subjected to taper etching is used in a minute flow path of a liquid in a system called a micro TAS (Total Analysis System). Also, a V-grooved silicon body is used as a base for placing a fine optical fiber. In such a silicon body, since a desired taper angle and smoothness of the taper surface are desired, it is necessary to satisfy this demand when producing a tapered silicon body by plasma etching.

Various techniques for etching a silicon material into a tapered shape have been proposed (see, for example, Patent Document 1). In the etching method of Patent Document 1, a mixed gas of chlorine gas as an etching gas, methane gas as a deposition gas, and oxygen gas is used, and a tapered shape is created by methane gas (deposition gas). . Further, oxygen gas is added in order to eliminate the difference in taper shape caused by the pattern size of the etching mask.
Japanese Patent Laid-Open No. 61-247033

When plasma etching is performed on a silicon material having an etching mask formed on the surface using SF ₆ gas as a process gas, the boundary between the tapered surface and the flat surface is rounded because the isotropic etching is strong. In addition, the roughness of the taper surface exceeded 200 nm. The roughness of the taper surface represents the degree of unevenness of the taper surface, and specifically indicates the distance between the uppermost surface and the lowermost surface (peak to valley). Further, when plasma etching is performed on a silicon material having an etching mask formed on the surface using a mixed gas of an etching gas and a deposition gas as a process gas, for example, SF ₆ = 130 sccm and C ₄ F ₈ = 30 sccm. An acute taper shape with a taper angle of 65 ° under flow conditions could be formed, but it was difficult to control the taper angle to a desired angle, and the roughness of the taper surface exceeded 200 nm. Thus, in the conventional technique, it is difficult to control the taper angle to a desired value, and there is a problem that the roughness of the taper surface cannot be reduced. Further, the conventional technique has a problem that an overhang shape is formed at the interface between the silicon material 21 and the mask 22 as shown in FIG.

  In Patent Document 1, since the taper shape is created by the deposition gas, there is a problem in that the reproducibility is lacking, for example, the etching rate is lowered or the deposition process proceeds too much to stop the etching. Further, oxygen gas is only added for the purpose of destroying the polymer of the deposition gas, and control for forming a desired taper angle cannot be performed.

  The present invention has been made in view of such circumstances. A silicon etching method and apparatus capable of easily achieving a desired taper angle, realizing a smoothed taper surface, and causing no overhang shape, and thereby It aims at providing the produced etching silicon body.

The silicon etching method according to the present invention is a method in which a silicon material to be etched, on which an etching mask is formed, is placed in an atmosphere into which a process gas is introduced, and the silicon material is etched in a tapered shape by plasma of the process gas. As the process gas, a mixture of a first gas for etching, a fluorocarbon-based second gas for deposition, and oxygen gas is used, and the flow rate of the second gas or oxygen gas is made constant. by adjusting the flow rate ratio of the oxygen gas to the flow rate of the second gas in the range of 0 to 2.5 in the state, and controlling the taper angle of the silicon material after etching.

The silicon etching apparatus according to the present invention is an apparatus in which a silicon material to be etched with an etching mask formed therein is placed in a reactor into which a process gas is introduced, and the silicon material is etched in a tapered shape by the plasma of the process gas. A first gas introducing means for introducing a first gas for etching into the reactor, a second gas introducing means for introducing a second fluorocarbon-based gas for deposition into the reactor, and oxygen Third gas introduction means for introducing gas into the reactor, and introduction of the second gas into the reactor with a constant introduction amount of the second gas or oxygen gas into the reactor. Adjusting means for adjusting the ratio of the amount of the oxygen gas introduced into the reactor to the amount within a range of 0 to 2.5, and the first gas and the second gas introduced into the reactor as well as A mixed gas of serial oxygen gas as used as the process gas, is characterized in that so as to control the taper angle of the silicon material after the etching by the adjustment in the adjustment means.

In the present invention, as a process gas for plasma etching a silicon material, a mixture of a first gas for etching, a second fluorocarbon-based gas (for example, C ₄ F ₈ ) and oxygen gas is used. Use gas. The fluorocarbon polymer formed with the second gas is destroyed with oxygen plasma, and the silicon material is etched into a tapered shape. Therefore, a taper with a small surface roughness can be easily formed.

  In the present invention, the taper angle is controlled by adjusting the flow rate of the added second gas and / or oxygen gas. When the flow rates of the first gas and the oxygen gas are constant, when the taper angle is close to 85 ° (the taper surface is nearly vertical), the flow rate of the second gas is increased and the taper angle is separated from 85 ° (the taper surface is When it is greatly inclined), the flow rate of the second gas is reduced. When the flow rates of the first gas and the second gas are constant, the flow rate of oxygen gas is decreased when the taper angle is close to 85 °, and the flow rate of oxygen gas is increased when the taper angle is away from 85 °. Therefore, a desired taper angle can be easily realized, and specifically, the taper angle can be easily controlled from 55 ° to 85 ° by adjusting the flow rate of these gases.

  The silicon etching method according to the present invention is characterized in that a ratio of the flow rate of the oxygen gas to the flow rate of the second gas is 0.5 or more.

  In the present invention, the flow rate of oxygen gas is 0.5 times or more the flow rate of the second gas. By doing so, the roughness of the taper surface can be reduced to less than 50 nm.

  The silicon etching method according to the present invention is characterized in that a ratio of the flow rate of the oxygen gas to the flow rate of the second gas is 2 or more.

  In the present invention, the flow rate of oxygen gas is set to at least twice the flow rate of the second gas. By doing so, an overhang shape does not occur at the interface between the silicon material and the etching mask.

  The silicon etching method according to the present invention is characterized in that the area of the etched silicon material in contact with the etching mask is smaller than the area of the etching mask.

  In the present invention, the taper shape is created by destroying the polymer of the second gas for deposition with plasma of oxygen gas. Therefore, the polymer of the second gas is destroyed by the oxygen plasma, and the area of the etched silicon material in contact with the etching mask becomes smaller than the area of the etching mask.

An etched silicon body according to the present invention is an etched silicon body etched by any of the silicon etching methods according to the present invention using the silicon etching apparatus according to the present invention, wherein the taper angle is 55 ° or more. It is 85 degrees or less, and the taper surface roughness is less than 50 nm.

  The present invention provides an etched silicon body having a taper angle of 55 ° to 85 ° and a taper surface roughness of less than 50 nm. Such an etched silicon body can be used as a member such as a fine liquid flow path or a fine optical fiber mounting table.

  In the present invention, a mixed gas of the first gas for etching, the second fluorocarbon-based gas for deposition, and the oxygen gas is used as the process gas when the silicon material is plasma-etched. A tapered shape with small roughness can be easily formed.

  In the present invention, the taper angle is controlled by adjusting the flow rate of the added oxygen gas and / or the second gas for deposition, so that the desired taper angle can be easily realized.

  In the present invention, since the ratio of the flow rate of the oxygen gas to the flow rate of the second gas is 0.5 times or more, the roughness of the taper surface can be reduced to less than 50 nm.

  In the present invention, since the ratio of the flow rate of the oxygen gas to the flow rate of the second gas is set to be twice or more, the occurrence of an overhang shape at the interface between the silicon material and the etching mask can be prevented.

  Furthermore, in the present invention, an etched silicon body having a taper angle of 55 ° to 85 ° and a taper surface roughness of less than 50 nm can be provided. It can be used as a member such as a table.

FIG. 1 is a diagram showing a state in which an overhang shape is formed.
FIG. 2 is a configuration diagram of an example of a plasma etching apparatus for performing a silicon etching method according to the present invention.
FIG. 3 is a diagram showing a silicon etching process.
[FIG. 4] It is a block diagram of the other example of the plasma etching apparatus for enforcing the silicon etching method based on this invention.
FIG. 5 is a view showing an example of an etched silicon body produced by the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor 2a Plasma generation chamber 2b Reaction chamber 3 Coil 4 Gas introduction pipe 6 Platen 8,10 High frequency power supply 11 Substrate electrode 14a, 14b, 14c Gas pipe 15a, 15b, 15c Mass flow controller (MFC)
20 Sample 21 Silicon material 22 Etching mask 30 Etching silicon body

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
FIG. 2 is a configuration diagram of an example of a plasma etching apparatus for carrying out the silicon etching method according to the present invention. The plasma etching apparatus shown in FIG. 2 is an inductively coupled plasma apparatus (ICP (Inductively Coupled Plasma) apparatus) that independently controls plasma generation and plasma drawing.

  In FIG. 2, reference numeral 1 denotes a reactor. The reactor 1 performs plasma etching on the upper plasma generation chamber 2 a that generates plasma by energizing the coil 3 and the sample 20 by drawing the generated plasma. A reaction chamber 2b on the lower side.

  The plasma generation chamber 2a has a shape of a ceramic hollow cylinder, and a coil 3 is concentrically surrounded on the peripheral surface thereof. A high frequency power source 8 is connected to the coil 3 via a matching circuit 7. A gas introduction pipe 4 for introducing a process gas into the reactor 1 is connected to the center of the upper wall of the plasma generation chamber 2a so as to penetrate therethrough. A process gas plasma is generated in the plasma generation chamber 2a by applying an AC voltage to the coil 3.

The gas introduction pipe 4 is branched into three gas pipes 14a, 14b and 14c. The gas pipes 14a, 14b and 14c are SF ₆ gas source, C ₄ F ₈ gas source and O ₂ gas source (whichever (Not shown). As a result, a gas mixture of SF ₆ gas as the first gas for etching, C ₄ F ₈ gas as the second fluorocarbon-based gas for deposition, and O ₂ gas is used as the process gas in the reactor 1. It has been introduced inside. In the middle of each gas pipe 14a, 14b, 14c, mass flow controllers (MFC) 15a, 15b, 15c for controlling the flow rate of each gas are provided. Each of these mass flow controllers 15a, 15b, 15c controls the flow rate of each corresponding gas based on the control signal from the control unit 16.

  An exhaust port 5 connected to an exhaust device (not shown) is opened on the side wall of the reaction chamber 2b. A platen 6 having a substrate electrode 11 on which a sample 20 to be etched is placed is disposed at the bottom of the reaction chamber 2b. A high frequency power supply 10 is connected to the platen 6 via a matching circuit 9. The plasma generated in the plasma generation chamber 2a is drawn into the reaction chamber 2b by applying an alternating voltage to the substrate electrode 11, and the sample 20 is etched by the drawn plasma.

  Next, silicon etching according to the present invention using the plasma etching apparatus having such a configuration will be described. FIG. 3 is a diagram showing a silicon etching process.

  First, a sample 20 as shown in FIG. A photoresist serving as a mask material is applied on the silicon material 21, and an etching mask 22 is patterned in a region other than the etching target by an exposure process. A sample 20 in which an etching mask 22 is formed on a silicon material 21 is placed on the platen 6.

The inside of the reactor 1 is depressurized by an exhaust device (not shown) through the exhaust port 5, and process gas (mixed gas of SF ₆ , C ₄ F ₈ and O ₂ ) is supplied from the gas introduction pipe 4 into the plasma generation chamber 2 a. To introduce. At this time, the flow rates of SF ₆ gas, C ₄ F ₈ gas, and O ₂ gas are controlled by the mass flow controllers 15a, 15b, and 15c, respectively. The pressure of the mixed gas is about 4.0 Pa. In the present invention, the flow rate of the O ₂ gas is 0.5 times or more, more preferably 2 times or more the flow rate of the C ₄ F ₈ gas. This can be achieved by the flow rate of _{O 2} gas and _C 4 _{F 8} gas flow rate of 0.5 times or more, it is possible to reduce the roughness of the tapered surface to below 50 nm, also the flow rate of _{O 2} gas _C 4 F This is because an overhang shape can be prevented from occurring at the interface between the silicon material and the etching mask by setting the flow rate of ₈ gases to at least twice.

  Then, an AC voltage (applied power: about 1700 W) is applied to the coil 3 from the high frequency power supply 8 via the matching circuit 7 to generate plasma of a process gas in the plasma generation chamber 2a, and at the same time, a matching circuit is applied to the substrate electrode 11. An AC voltage (applied power: about 50 W) is applied from the high-frequency power source 10 through 9 and the generated plasma is drawn into the reaction chamber 2b, and the etching mask 22 is applied to the region other than the etching target by the drawn plasma. The silicon material 21 of the sample 20 on which is formed is etched. At this time, the thickness of the etched region in the silicon material 21 is, for example, 5 μm to several hundred μm.

By such etching, an etched silicon body 30 having a taper angle θ can be produced as shown in FIG. Further, in the manufactured etched silicon body 30, an overhang shape is not seen at the interface between the silicon material 21 and the etching mask 22, and a smooth tapered surface is obtained as a whole. In the present invention, since the O ₂ plasma acts so as to destroy the C ₄ F ₈ polymer, the area of the upper surface of the etching silicon body 30 (the surface in contact with the etching mask 22) is smaller than the area of the etching mask 22. Become. On the other hand, in the etching method of Patent Document 1, the area of the upper surface of the etching silicon body (the surface on the side in contact with the etching mask) is larger than the area of the etching mask.

Hereinafter, examples and comparative examples of the present invention in which the silicon material 21 is etched by specifically controlling the flow rates of the C ₄ F ₈ gas and the O ₂ gas with the flow rate of the SF ₆ gas being constant will be described.

(Comparative Example 1)
When etching is performed using a mixed gas of SF ₆ = 70 sccm, C ₄ F ₈ = 200 sccm, and O ₂ = 0 sccm as the process gas, the taper angle θ = 90 ° and the taper surface roughness is less than 10 nm. A silicon body 30 was produced. That is, an etched silicon body 30 having vertical sidewalls was produced.

When etching is performed using a mixed gas of SF ₆ = 70 sccm, C ₄ F ₈ = 200 sccm, and O ₂ = 100 sccm (O ₂ flow rate / C ₄ F ₈ flow rate = 0.5) as the process gas, the taper angle θ An etched silicon body 30 having a taper surface roughness of less than 50 nm was prepared. However, an overhang shape was observed at the interface between the silicon material 21 and the etching mask 22.

When etching is performed using a mixed gas (O ₂ flow rate / C ₄ F ₈ flow rate = 2.5) of SF ₆ = 70 sccm, C ₄ F ₈ = 200 sccm, and O ₂ = 500 sccm as the process gas, the taper angle θ An etched silicon body 30 having a taper surface roughness of less than 10 nm was produced. No overhang shape was observed at the interface between the silicon material 21 and the etching mask 22.

When etching is performed using a mixed gas of SF ₆ = 70 sccm, C ₄ F ₈ = 250 sccm, and O ₂ = 500 sccm (O ₂ flow rate / C ₄ F ₈ flow rate = 2) as the process gas, the taper angle θ = 75. An etched silicon body 30 having a taper surface roughness of less than 20 nm was produced. No overhang shape was observed at the interface between the silicon material 21 and the etching mask 22.

When etching is performed using a mixed gas (O ₂ flow rate / C ₄ F ₈ flow rate = 1.4) of SF ₆ = 70 sccm, C ₄ F ₈ = 350 sccm, and O ₂ = 500 sccm as the process gas, the taper angle θ An etched silicon body 30 having a taper surface roughness of less than 10 nm was prepared. However, an overhang shape was observed at the interface between the silicon material 21 and the etching mask 22.

In the comparative example and Examples 1 to 4, there was almost no variation in the etching rate due to the flow rate of O ₂ .

From the results of the comparative example and Examples 1 and 2, it can be seen that the taper angle θ can be controlled by adjusting the flow rate of the O ₂ gas. Specifically, the taper angle can be changed from 85 ° to 65 ° by changing the flow rate of O ₂ gas from 0 sccm to 500 sccm. Therefore, a desired taper angle can be realized by adjusting the flow rate of O ₂ gas.

From the results of Examples 2 to 4, it can be seen that the taper angle θ can be controlled by adjusting the flow rate of the C ₄ F ₈ gas. Specifically, the taper angle can be changed from 65 ° to 85 ° by changing the flow rate of C ₄ F ₈ gas from 200 sccm to 350 sccm while the flow rate of O ₂ gas is constant 500 sccm. Therefore, a desired taper angle can be realized by adjusting the flow rate of the C ₄ F ₈ gas while adding a predetermined amount of O ₂ gas.

From the results of Examples 1 to _4, by a C 4 _{F 8 O 2} gas flow rate ratio of the relative flow rate of gas 0.5 or more, it can be seen that the roughness of the tapered surface can be controlled to less than 50nm. Further, in Examples 2 to 4 in which the flow rate ratio is further increased, the roughness of the taper surface can be reduced to less than 20 nm. Therefore, if the ratio of O ₂ flow rate / C ₄ F ₈ flow rate is set to 0.5 or more, the taper surface can always be smoothed even if the taper angle is freely controlled.

From the results of Examples 1 to 4, by the C ₄ F ₈ O ₂ gas flow rate ratio of the relative flow rates of the gas and more, it can be seen that can prevent the occurrence of overhangs. As a result of further experiments, the applied voltage to the coil 3 is 1200 W, and the process gas is a mixed gas of SF ₆ = 20 sccm, C ₄ F ₈ = 40 sccm, O ₂ = 90 sccm (O ₂ flow rate / C ₄ F ₈ flow rate = When etching was performed using 2.3), an etched silicon body 30 having a taper angle θ = 65 ° and a taper surface roughness of less than 20 nm, in which no overhang shape was observed, was produced. On the other hand, in the case of O ₂ flow rate / C ₄ F ₈ flow rate = 0.5 and in the case of O ₂ flow rate / C ₄ F ₈ flow rate = 1.5, the etched silicon body 30 in which an overhang shape is seen is obtained. It was made. Therefore, by setting the ratio of O ₂ flow rate / C ₄ F ₈ flow rate to 2 or more, it is possible to form a taper surface with good linearity in which no overhang shape is observed.

From the above, in the present invention, the taper angle can be easily controlled to form a desired taper angle, and the taper shape is such that the surface roughness is small and smooth, and no overhang is observed. An etched silicon body can be produced. Specifically, an etched silicon body having an overhang hang shape having a taper angle of 65 ° to 85 ° and a taper surface roughness of less than 50 nm can be produced. Further, it is possible to reduce the roughness of the taper surface to less than 10 nm by increasing the flow rate of O ₂ gas.

  FIG. 4 is a configuration diagram of another example of a plasma etching apparatus for carrying out the silicon etching method according to the present invention. The plasma etching apparatus shown in FIG. 4 is a plasma apparatus that performs plasma generation and etching processing in one chamber (inside the reactor 1). 4, the same reference numerals are given to the same or the same parts as those in FIG.

  The reactor 1 has a shape of a ceramic hollow cylinder, and a coil 3 is concentrically surrounded on its peripheral surface. A high frequency power source 8 is connected to the coil 3 via a matching circuit 7. A gas introduction pipe 4 for introducing a process gas into the reactor 1 is connected to the center of the upper wall of the reactor 1 in a penetrating manner. Then, plasma of a process gas is generated in the reactor 1 by applying an alternating voltage to the coil 3.

The gas introduction pipe 4 is branched into three gas pipes 14a, 14b and 14c. The gas pipes 14a, 14b and 14c are SF ₆ gas source, C ₄ F ₈ gas source and O ₂ gas source (whichever (Not shown). As a result, a gas mixture of SF ₆ gas as the first gas for etching, C ₄ F ₈ gas as the second fluorocarbon-based gas for deposition, and O ₂ gas is used as the process gas in the reactor 1. It has been introduced inside. In the middle of each gas pipe 14a, 14b, 14c, mass flow controllers (MFC) 15a, 15b, 15c for controlling the flow rate of each gas are provided. Each of these mass flow controllers 15a, 15b, 15c controls the flow rate of each corresponding gas based on the control signal from the control unit 16.

  An exhaust port 5 connected to an exhaust device (not shown) is opened on the side wall of the reactor 1. A platen 6 having a substrate electrode 11 on which a sample 20 to be etched is placed is disposed at the bottom of the reactor 1. A high frequency power supply 10 is connected to the platen 6 via a matching circuit 9. The plasma generated in the reactor 1 is drawn downward by the application of an alternating voltage to the substrate electrode 11, and the sample 20 is etched by the drawn plasma.

An example in which silicon etching is performed using the plasma apparatus having such a configuration will be described. The inside of the reactor 1 is decompressed by an exhaust device (not shown) through the exhaust port 5, and the process gas (SF ₆ gas: flow rate 50 sccm, C ₄ F ₈ gas: flow rate 40 sccm and O ₂ gas: A mixed gas having a flow rate of 85 sccm) is introduced into the reactor 1. Then, an AC voltage (applied power: about 900 W) is applied to the coil 3 via the matching circuit 7 from the high frequency power supply 8 to generate plasma of the process gas in the reactor 1, and at the same time, the matching circuit 9 is applied to the substrate electrode 11. A sample in which an AC voltage (applied power: about 25 W) is applied from the high-frequency power source 10 through the plasma, the generated plasma is drawn downward, and the etching mask 22 is formed in a region other than the etching target by the drawn plasma. Twenty silicon materials 21 were etched. As a result, an etched silicon body 30 in which the taper angle θ = 55 °, the roughness of the taper surface was less than 20 nm, and no overhang shape was observed was produced.

  In the above-described example, the case where etching is performed so as to form a trapezoidal shape in a cross-sectional view has been described.

Further, since the taper shape can be etched by adding O ₂ gas, the etching process is performed in two stages, and in the first stage, an etching gas (for example, SF ₆ ) and a deposition gas (for example, C _4). By using a mixed gas of only F ₈ ) and using a mixed gas of an etching gas (for example, SF ₆ ), a deposition gas (for example, C ₄ F ₈ ), and an O ₂ gas in the second stage, FIG. As shown in FIG. 5, an etched silicon body 30 having an etching shape in which the lower portion 30a is not tapered and the upper portion 30b has a tapered surface can be produced.

In the above-described example, the case where SF ₆ is used as the etching gas and C ₄ F ₈ is used as the deposition gas has been described. However, the present invention is not limited to this. As an etching gas, a gas represented by a general formula SF _x such as SF ₄ can be used in addition to SF ₆ . Further, as the deposition gas, in addition to C ₄ F ₈ , a gas represented by a general formula C _x F _y such as C ₅ F ₈ or a general formula C _x H _y F _z such as CHF ₃ or CH ₂ F ₂ is used. The indicated gas can be used.

Claims (6)

In the method of setting the etching target silicon material on which the etching mask is formed in an atmosphere into which a process gas is introduced, and etching the silicon material in a taper shape by the plasma of the process gas,
As the process gas, a mixture of a first gas for etching, a fluorocarbon-based second gas for deposition, and oxygen gas is used, and the flow rate of the second gas or oxygen gas is made constant. A tape etching angle of the silicon material after etching is controlled by adjusting a ratio of a flow rate of the oxygen gas to a flow rate of the second gas in a range of 0 to 2.5 in a state. .   The silicon etching method according to claim 1, wherein a ratio of the flow rate of the oxygen gas to the flow rate of the second gas is 0.5 or more.   2. The silicon etching method according to claim 1, wherein a ratio of a flow rate of the oxygen gas to a flow rate of the second gas is set to 2 or more.   The silicon etching method according to any one of claims 1 to 3, wherein an area of the silicon material after etching that is in contact with the etching mask is smaller than an area of the etching mask. In an apparatus in which a silicon material to be etched, in which an etching mask is formed, is installed in a reactor into which a process gas is introduced, and the silicon material is etched into a tapered shape by the plasma of the process gas.
First gas introduction means for introducing a first gas for etching into the reactor, second gas introduction means for introducing a second fluorocarbon-based gas for deposition into the reactor, and oxygen gas Third gas introduction means for introducing into the reactor, and with respect to the introduction amount of the second gas into the reactor in a state where the introduction amount of the second gas or oxygen gas into the reactor is constant . Adjusting means for adjusting the ratio of the amount of oxygen gas introduced into the reactor in the range of 0 to 2.5, the first gas introduced into the reactor, the second gas, and the A silicon etching apparatus characterized in that a mixed gas of oxygen gas is used as the process gas, and the taper angle of the silicon material after etching is controlled by adjustment by the adjusting means. An etched silicon body etched by the silicon etching method according to any one of claims 1 to 4 using the silicon etching apparatus according to claim 5, wherein the taper angle is not less than 55 ° and not more than 85 °. An etched silicon body having a surface roughness of less than 50 nm.

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